1. Field of the Invention
The present invention relates generally to the fabrication of semiconductor devices and to chemical mechanical polishing and planarization of semiconductor devices.
2. Description of the Related Art
In the fabrication of integrated circuits and other electronic devices, multiple layers of conducting, semiconducting, and dielectric materials are deposited on or removed from a surface of a substrate. Thin layers of conducting, semiconducting, and dielectric materials may be deposited by a number of deposition techniques. Common deposition techniques in modern processing include physical vapor deposition (PVD), also known as sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and now electrochemical plating (ECP).
As layers of materials are sequentially deposited and removed, the uppermost surface of the substrate may become non-planar across its surface and require planarization. Planarizing a surface, or “polishing” a surface, is a process where material is removed from the surface of the substrate to form a generally even, planar surface. Planarization is useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, scratches, and contaminated layers or materials. Planarization is also useful in forming features on a substrate by removing excess deposited material, such as copper containing material, used to fill the features and to provide an even surface for subsequent levels of metallization and processing.
Chemical mechanical planarization, or chemical mechanical polishing (CMP), is common technique used to planarize substrates. CMP utilizes a chemical composition, typically a slurry or other fluid medium, for selective removal of material from substrates. In conventional CMP techniques, a substrate carrier or polishing head is mounted on a carrier assembly and positioned in contact with a polishing pad in a CMP apparatus. The carrier assembly provides a controllable pressure to the substrate urging the substrate against the polishing pad. The pad is moved relative to the substrate by an external driving force. Thus, the CMP apparatus effects polishing or rubbing movement between the surface of the substrate and the polishing pad while dispersing a polishing composition, or slurry, to effect both chemical activity and mechanical activity.
Conventional CMP processes are performed using an abrasive article, such as a polishing composition, or slurry, containing abrasive particles in a reactive solution with a conventional polishing pad. Alternatively, the abrasive article can be a fixed abrasive article, such as a fixed abrasive polishing pad, which may be used with a, CMP composition or slurry that does not contain abrasive particles, often referred to as an abrasive free composition. A fixed abrasive article typically comprises a backing sheet with a plurality of geometric abrasive composite elements adhered thereto. Alternatively, the CMP processes can be performed in the absence of an abrasive article, such as by the use of an abrasive free composition with a conventional polishing pad.
Conventionally, in polishing substrate features, such as a dual damascenes features formed by the deposition of a barrier layer in an aperture and, for example, a copper containing material disposed on the barrier layer, excess copper containing material is polished to the barrier layer, and then the barrier layer is polished to the underlying dielectric layer to form the feature. Excess copper containing material is broadly defined herein copper containing material deposited on the substrate in an amount more than sufficient to substantially fill features formed on the substrate surface. Generally, all of the excess copper containing material is removed from the surface of the barrier layer prior to polishing the barrier layer.
However, the interface between the copper containing material and the barrier layer is generally non-planar and is difficult to sufficiently remove all of the excess copper containing material. Additionally, the copper containing material polishing process often removes the excess copper containing material and the barrier materials at different rates which may result in the formation of topographical defects in the substrate surface while still not sufficiently removing excess copper containing material from the barrier layer. Further, some polishing compositions, such as some abrasive free polishing compositions, have difficulty removing a satisfactory amount of excess copper containing material from the substrate surface. As such, many copper removal processes result in residual copper containing material being retained on the barrier layer and substrate surface. The retention of residual copper containing material has been observed to detrimentally affect subsequent polishing processes and detrimentally affect the polish quality of the substrate surface.
One method to ensure removal of all the excess copper containing material before removing the barrier material is to overpolish the deposited copper containing material. Overpolishing may result in dishing of the copper containing material in the features formed on the surface of the substrate. Dishing occurs when a portion of the surface of a metal deposited in an aperture or other substrate structure formed in a dielectric layer is excessively polished resulting in the formation topographical defects, such as concavities or depressions in the copper containing material on the substrate surface, and can further lead to non-uniform removal of the barrier layer disposed thereunder. Dishing performance is used to describe the ability of a CMP composition or process to polish and planarize a surface without dishing or with reduced dishing of the surface. Additionally, in some CMP composition, such as some abrasive free compositions, the application of overpolishing techniques have not been completely successful in removing all of the excess copper containing material from the surface of the substrate.
Therefore, there exists a need for a method and CMP composition that reduces or removes residual copper containing materials during CMP processing.